JP2544400B2 - Injection head for producing multi-layer moldings from thermoplastic synthetic resin materials - Google Patents

Abstract

The objects produced have a core, for example of foamed thermoplastic material, and an outer skin of, for example, unfoamed thermoplastic material. The intention is to reduce the structural complexity and at the same time ensure that on the one hand mouldings of relatively large volume can be produced reliably and dimensionally stably with reduced material requirement, but on the other hand it is also ensured that the so-called holding pressure can be exerted reliably on the plastics moulding formed in the injection mould. Using an injection head 1, in which on the one hand an inner nozzle 13, 14, 15 for the one material is formed by a tubular insert 7, guided axially displaceably in the housing 4, and in turn contains a likewise axially displaceable needle 9 as shut-off device, and in which an annular nozzle 10, 11 for the other material is formed by an annular space 6 between the tubular insert 7 and the housing 4, and in which finally the shut-off needle 9 has at its free end an extension 18, which in the shut-off position of the inner nozzle 13, 14, 15 terminates at least flush with the free end of the tubular insert 7, this is achieved by the shut-off needle 9 containing at its free end 19 a central nozzle opening 20, which is adjoined to the rear by a connecting channel 21, which has a radial peripheral opening 22. In the wall of the tubular insert 7 there is likewise a longitudinally running connecting channel 24, which has on the inner periphery 8 of the tubular insert 7 a radial mouth 23. At least in the axial position of the shut-off needle 9 corresponding to the shut-off position, the radial peripheral opening 22 of the connecting channel 21 of the shut-off needle 9 can be set, according to choice, into and out of flow connection with the radial mouth 23 of the connecting channel 24 in the tubular insert 7 by relative turning about the common longitudinal axis. <IMAGE>

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an inner nozzle for one synthetic resin material, which is formed by a tubular insert slidably guided in a casing in an axial direction, The inner nozzle is equipped with a needle as a closure device that is axially slidable, and an annular nozzle for other synthetic resin materials is formed by the annular gap between the tubular insert and the casing and is axially slidable Tubular insert forms the closure device of the annular nozzle, the needle has a projection at its free end, which at least is flush with the free end of the tubular insert in the closed position of the inner nozzle. The present invention relates to an injection head for producing a multilayer molded body having a core made of, for example, a foamed thermoplastic synthetic resin and an outer skin made of, for example, a non-foamed thermoplastic material.

[Conventional technology and its drawbacks]

This type of injection head is disclosed in, for example, West German Patent Publication No. 225981.
It is already known from No. 8 and West German Patent Publication No. 2342789. In this case, the injection head is not only simple in construction, but also the surplus protruding in the injection head is prevented from remaining when it is used, and the drawbacks associated therewith are avoided. That is, the work cost conventionally required for removing the surplus is unnecessary, and a completely closed outer shell made of synthetic resin that does not foam is formed around the foam core of the molded body. Further, the molded body can be easily released from the mold by opening the mold.

Injection heads for producing multi-layer moldings, which in principle have the same construction, are already known. This molded body is formed by two or more, especially three thermoplastic synthetic resin materials which are sequentially supplied to the mold (see West German Patent Application Publication Nos. 2247995 and 2346135).

In this case, in the injection head, two tubular inserts are arranged around the inner nozzle so as to additionally form two annular nozzles. Within this tubular nozzle, each tubular insert acts as a closure device.

Due to this structure, the injection head has a relatively large outer diameter. Therefore, the ejection head cannot always be used without problems. In this case, further, a difficulty occurs when the molded body formed by the mold is repressurized. This is because, in the case of an injection head formed in this way for processing three different synthetic resin materials, the regular supply of synthetic resin material used according to the standard is questionable.

[Problems of the Invention]

The underlying problem of the invention is to provide an injection head of the kind mentioned at the outset, which guarantees a low-cost production of a stable, multi-layer compact of relatively small structural dimensions, of simple construction and of light weight and large volume. Is to provide.

[Structure of Invention]

According to the invention, according to the invention, the closing needle has, at the end of its protrusion, a central nozzle opening, a connection passage is connected to the rear side of the nozzle opening, the connection passage having a radial opening, In the wall of the tubular insert there is likewise formed a longitudinally extending connecting passage, which opens radially at the inner circumference of the tubular insert and the radial opening of the connecting passage of the needle is It is solved by being able to selectively connect or disconnect with the radial opening of the connecting passage of the tubular insert by relative rotation about a common longitudinal axis, at least in the axial position of the needle corresponding to the closed position.

[Advantages of the Invention] An advantage of the above-described configuration of the injection head according to the present invention is that it is only necessary to provide the injection head with one annular nozzle, although three material components can be processed. Therefore, the injection head can be manufactured with a small cross-sectional size and at a minimum structural cost.

Further, the third material component can be optionally supplied to the molding die during the injection process. That is, the third material component can be supplied to the molding die not only alone, but after each of the other two material components in any order. Furthermore, all material components can be fed to the molding tool simultaneously.

[Embodiments of the invention and its effects]

In an embodiment of the invention, the axial length of the radial opening of the connecting passage in the needle and / or the radial opening of the connecting passage in the tubular insert is determined according to the effective length of the protrusion of the needle, When the needle is in any axial position relative to the tubular insert, a connection between the radial opening of the connecting passage in the needle and the radial opening of the connecting passage in the insert is possible.

However, the radial opening of the connecting passage in the needle and / or the radial opening of the connecting passage in the tubular insert may have different circumferential lengths in different axial extents.

By these means, the supply of the third material component to the molding die can be varied within wide limits.

In the case of the injection head according to the invention which has been demonstrated, the connecting passages in the needle and the tubular insert form a gas passage, in which the radial openings of the connecting passages act as rotary slider isolation valves with each other. To do. In that case, in the simplest case, air is forced into the mold as working gas. In this case, the synthetic resin material supplied in advance to the molding die is pressed against the wall of the molding die while forming the hollow chamber, which results in the formation of a relatively thin wall even though the shape is very stable. A molded body is formed.

From a structural point of view, it is recommended that the needle is axially slidable and rotatable. The tubular insert may be provided exclusively axially slidably.

Furthermore, it is preferred that the rotation angle of the needle is or can be limited. In this case, the rotation angle of the needle may be restricted or limitable differently at different axial positions.

The optimum function of the injection head according to the invention is achieved in that the actuator for the tubular insert and the actuator for the needle can be controlled, for example by displacement, by means of both injection pistons supplying different synthetic resin materials. It

〔Example〕

 The drawing shows an embodiment of the object of the invention.

The figure shows an injection head 1 of an apparatus for producing a synthetic resin molding. This injection head has a sprue bush 3 (not shown) through its nozzle orifice 2.
Can be attached to.

In the casing 4 of the injection head 1, a passage 5 is formed coaxially with the nozzle orifice 2. A tubular insert 7 is accommodated in this passage so as to be slidable while being restricted in the axial direction while forming an annular gap 6. In the tubular insert 7, a needle 9 is guided in close contact with the inner circumference 8 of the insert so as to be axially restricted and slidable. The tubular insert 7 and needle 9
It has a shaft (not shown) guided to the rear side through the injection head 1. Sliding drive devices act on the shafts. The sliding drive can be operated, for example, with a pressure medium, in particular hydraulically.

The front end of the tubular insert 7 is provided with a conical seal 10. When the tubular insert 7 is in the sealing position where the tubular insert 7 slides forward (see FIG. 1),
It cooperates with the corresponding conical sealing part 11 of the nozzle orifice 2, in which case the annular gap 6 is brought into the outlet 12 of the nozzle orifice 2.
Shut off against.

By retracting the tubular insert 7 axially by means of its sliding drive, the conical seal part 10 is separated from the conical seal part 11, whereby the annular gap 6 is the outlet.
Communicates with 12 (see Figure 2). Therefore, the thermoplastic synthetic resin material therein can reach the injection mold.
The annular gap 6 and the conical seal portions 10, 11 form an annular nozzle.

The needle 9 also has a conical seal portion 13. This seal contacts the corresponding conical seal 14 of the tubular insert 7 in the forward sliding position of the needle 9. As a result, the gap between the inner peripheral portion 8 of the insert and the central passage port 15 is cut off.

As can be clearly seen from FIGS. 1 to 5, the inner peripheral portion 8 of the tubular insert 7 is close to the conical seal portion 14.
The opening of the supply passage 17 for the second thermoplastic synthetic resin material.
16 are provided. The supply passage 17 then extends longitudinally through the tubular insert 7, the rear end of which is connected to the injection unit for the thermoplastic synthetic resin material in question. A corresponding injection unit for the thermoplastic material is of course also connected to the annular gap 6 between the casing 4 and the tubular insert 7.

The supply passage 17, the conical seal portions 13 and 14, and the passage port 15 form an inner nozzle.

An important structural feature is that the needle 9 is at its free end,
It has a small diameter protrusion 18. This protrusion enters the passage opening 15 of the tubular insert 7 when the needle 9 is in the forward sliding position.

When the needle 9 is in the forward sliding position, it is very advantageous if the end 19 of the projection 18 projects slightly from the passage opening 15 and is provided with a chamfer. This chamfer is formed in the direction of extension of the conical sealing part 10 of the tubular insert 7, with a slight entry into the outlet 12 of the nozzle orifice 2.

The needle 9 has a central nozzle opening 20 at the end 19 of its protrusion 18. A connection passage 21 is connected to the rear side of this nozzle opening. This connecting passage has a radial opening
With 22.

On the inner peripheral part 8 of the tubular insert 7, a radial opening 23 of the connecting passage 24 extending in the longitudinal direction is provided corresponding to the radial opening 22 of the connecting passage 21. This connecting passage 24
Is in the wall of the tubular insert 7 as well as the supply passage 17. Moreover, it is provided in the range of the transverse cross section that is diametrically opposed to the supply passage 17. At that time, the radial opening 23 of the connection passage 24 is axially farther from the conical seal portion 14 than the radial opening 16 of the supply passage 17.

The needle 9 is not only axially slidably guided in the tubular insert 7, but is also rotatably mounted in this insert at least with limited angular rotation.
For this purpose, it is connected to a rotary drive (not shown). This rotary drive can be operated, for example, by means of a pressure medium, in particular hydraulic pressure. This allows the radial opening 22 of the connecting passage 21 of the needle 9 to be selectively connected or disconnected to the radial opening 23 of the connecting passage 24 in the tubular insert 7.

In the case of the embodiment of the injection head 1 of FIGS. 1 to 4, the radial opening 22 of the connection passage 21 and the radial opening 23 of the connection passage 24 are located at the axial position where the needle 9 slides forward. The structure allows connection only at certain times.
However, in the case of FIG. 5, a radial opening 22 is formed so that the connection can be made in any axial position of the needle 9 with respect to the tubular insert 7.

As soon as the radial opening 22 of the connecting passage 21 overlaps the opening 23 of the connecting passage 24, it passes through the connecting passage 24 of the tubular insert 7 and the connecting passage 21 of the needle 9 from the central nozzle opening 20 of the injection head 1 in a thermoplastic synthesis. It is possible to supply resin materials. In this case, the connection passage 24 is connected to the injection unit for the thermoplastic synthetic resin material.

However, the central nozzle opening 20 particularly functions as follows. That is, as suggested in FIGS. 2 and 3, the synthetic resin material is first pushed into the injection mold from the annular gap 6 and then the synthetic resin material is pushed into the injection mold from the tubular insert 7, and then the gas is discharged. It serves, for example, to allow nitrogen or air to be supplied to the injection mold at a relatively high pressure.

In FIG. 2, from the annular gap 6 to the conical seal portions 10 and 11
The thermoplastic synthetic resin supplied to the injection mold through the annular nozzle between and the outlet 12 of the nozzle orifice 2 is a synthetic agent containing no foaming agent for forming a dense outer skin for the synthetic resin molded body. It is a resin. On the other hand, the thermoplastic synthetic resin material reaching the injection mold from the tubular insert 7 through the passage opening 15 and the outlet 12 is particularly a synthetic resin containing a foaming agent capable of forming a porous core of a synthetic resin molding. is there.

The respective axial position of the tubular insert 7 in the casing 4 of the injection head and the respective axial position and the respective rotational position of the needle 9 in the tubular insert 7 are determined by means of an associated sliding drive or rotation. Appropriate control of the drive system can be tailored to the individual requirements. In this case, the control signal can be derived from an injection unit or the like attached to the injection head 1.

In the case of the construction of the injection head according to FIGS. 1 to 4, when the inner nozzle formed by the supply passage 17, the conical seals 13, 14 and the passage opening 15 is brought into the closed position beforehand, Chisel, central nozzle opening in needle 9
20 allows medium supply to the injection mold (see Figure 4).
On the other hand, FIG. 5 shows another structural modification. In this case, for example, the axial length of the radial opening 22 of the connecting passage 21 in the needle 9 is such that this opening corresponds to the radial opening 23 of the connecting passage 24 of the tubular insert 7 in the closed and open positions of the inner nozzle. It is specified to be connected or disconnected. For that purpose, the needle 9 only has to be rotated relative to the tubular insert 7.

The same applies, of course, if the axial length of the radial opening 23 of the connecting passage 24 is correspondingly long, or if the radial opening 22 and the radial opening 23 are in harmony with each other and extend axially. The action is obtained.

The injection head 1 shown in the figure is used to manufacture a synthetic resin molding by a multi-component injection molding method. In doing so, it is possible to obtain the desired product properties with small structural dimensions and a minimum structural cost, and to use different synthetic resin materials to form the skin area and the core area. For example, the core region can be made of a reinforced synthetic resin material and the skin region or green region can be made of an unreinforced synthetic resin material. As a result, a good surface quality having high impact resistance due to the unreinforced synthetic resin material and a large steel property due to the reinforced synthetic resin material can be obtained.

However, moldings with a soft skin and a hard core can also be made.

Especially when making a molded product with a thick wall, the density of the molded product is important. This density is reduced by using the injection head 1 described above and adding many blowing agent additives to the synthetic resin material for forming the core. After the synthetic resin material has been put in the injection mold in advance, a relatively large amount of gas or air is press-fitted into the injection mold through the central nozzle opening to further reduce the density. That is, the gas or air forms a relatively large hollow chamber in the synthetic resin molded product.

The third medium supplied from the central nozzle opening 20 to the injection mold may be not only gas or air but also thermoplastic synthetic resin as described above. By means of this third medium, a so-called post-pressure is applied to the synthetic resin molding formed in the injection mould, which guarantees a complete and reliable finishing of this synthetic resin molding. The operation mode of the injection head 1 having the above-described structure shown in the drawing is as follows.

A predetermined amount of the first component of the thermoplastic synthetic resin is injected through the annular nozzle opened from the annular gap 6 (see FIG. 2).

Depending on the set operating position of the injection unit for the first component of the thermoplastic material, the inner nozzle is opened by sliding the needle 9 axially.

The annular nozzle for the first component of thermoplastic material is closed in a displacement and / or time-dependent manner.

Depending on the operating position of the injection unit for the second component of the thermoplastic material, the needle 9 is rotated into the open or passing position of the central nozzle opening 20 and thereby the third medium component ( Gas or air or thermoplastic synthetic resin).

Depending on the displacement or time of the injection unit, for example for the second component of the thermoplastic, the needle 9 is slid into its closed position.

The post-pressure applied to the molded body in the injection mold is generated in the molded body in the injection mold via the third medium component supplied through the central nozzle opening 20.

The control of the ejection head 1 can be performed in other ways, depending on the different desired target settings. Center nozzle opening 20
This can be achieved without axial sliding of the needle 9, so that no adverse material pushing into the injection mold takes place.

[Brief description of drawings]

Figure 1 shows all nozzles in their closed basic position,
A vertical sectional view of an injection head for producing a multi-layer molded body,
FIG. 2 shows the injection head with the annular nozzle opened, the same view as FIG. 1, FIG. 3 shows the injection head with the inner nozzle opened, and FIG. 4 shows the injection head with the central nozzle opened. FIG. 5 is a view showing an injection head that allows arbitrary opening and closing of the central nozzle when the annular nozzle is opened or closed and the inner nozzle is opened or closed. 1 ... Injection head 4 ... Casing 6 ... Annular gap 7 ... Insert 8 ... Inner circumference 9 ... Closing needle 18 ... Projection 19 ... Projection end 20 ... Nozzle opening 21 ... Connection passage 22 …… Radial opening 23 …… Radial opening 24 …… Connection passage

Claims (9)

(57) [Claims] 1. A closure device in which an inner nozzle for one synthetic resin material is axially slidably guided in a casing and is formed by a tubular insert, the inner nozzle being axially slidable. An annular nozzle for other synthetic resin material, which is provided by an annular gap between the tubular insert and the casing, and the axially slidable tubular insert forms a closing device for the annular nozzle. The needle has a protrusion at its free end, which at the closed position of the inner nozzle is at least flush with the free end of the tubular insert, for example a core made of foamed thermoplastic resin, For example, in an injection head for producing a multilayer molded body having an outer skin made of a thermoplastic material that does not foam, a needle (9) has an end (19) of a protrusion (18) thereof. , A central nozzle opening (20), a connection passage (21) being connected to the rear side of the nozzle opening, the connection passage having a radial opening (22), the wall of the tubular insert (7) A connecting passage (24) which also extends in the longitudinal direction is formed inside the connecting passage (24).
Radially open at the inner periphery (8) of the tubular insert (7), and the radial opening (22) of the connecting passageway (21) of the needle (9).
At least in the axial position of the needle corresponding to the closed position by a relative rotation about a common longitudinal axis, the radial opening (2) of the connecting passageway (24) of the tubular insert (7).
3) An injection head that can be selectively connected or disconnected. 2. The axial length of the radial opening (22) of the connecting passage (21) in the needle (9) and / or the radial opening (23) of the connecting passage (24) in the tubular insert (7). Is determined according to the effective length of the protrusion (18) of the needle (9) and the connection passage in the needle (9) is in any axial position with respect to the tubular insert (7). Injection head according to claim 1, characterized in that a connection between the radial opening (22) and the radial opening (23) of the connecting passage in the insert is possible. 3. Radial openings (22) of the connecting passages (21) in the needle (9) and / or radial openings (23) of the connecting passages (24) in the tubular insert (7) are of different axial directions. The ejection head according to claim 1, wherein the ejection head has different circumferential lengths within the range. 4. A needle (9) and a tubular insert (7).
The connecting passages (21, 24) inside form a gas passage, in which the radial opening (22, 24) of the connecting passage (21, 24) is formed.
The injection head according to any one of claims 1 to 3, characterized in that 3) act as rotary slider shutoff valves. 5. An injection head according to any one of claims 1 to 4, characterized in that the needle (9) is axially slidable and rotatable. 6. The injection head according to claim 1, characterized in that the tubular insert (7) is slidable exclusively in the axial direction. 7. The injection head as claimed in claim 1, characterized in that the rotation angle of the needle (9) is or can be limited. . 8. The rotation angle of the needle (9) is differently restricted or can be restricted at different axial positions, as claimed in claims 1 to 7. The injection head described in any one. 9. An actuator for a tubular insert (7) and an actuator for a needle (9) are controllable by an injection unit or the like for supplying different synthetic resin materials. Item 1 to 8
The injection head according to any one of items 1 to 10.